The invention relates generally to optical device structures. In particular, the invention relates to an optical waveguide and a method of making the same.
Optical waveguides or holograms are used for optical communication or information recording. In any type of optical communication system there is the need for interconnecting different discrete components. These components may include a range of devices, such as lasers, detectors, fibers, modulators, and switches. Polymer-based devices, such as waveguides, offer a viable way of interconnecting these components, and offer a potentially inexpensive interconnection scheme.
An optical waveguide provides an optical transmission path in which light propagates in a high refractive index medium surrounded with a low refractive index medium by undergoing a total reflection at its boundary surface. Here, the total reflection is the phenomenon in which, when the incident angle of light entering from a transparent high refractive index medium to a low refractive index medium is smaller than a certain angle, all the energy of the light is reflected at its boundary surface without loss. Holograms are interference fringes produced by exposing a photosensitive material to two light beams having high coherence. Holograms may be used in many applications, such as information recording media, reflecting plates, optical filters, and grating waveguides, by using the diffraction phenomenon of the interference fringe.
The most frequently used material for such a waveguide device is glass, which is formed into a fiber of specified dimensions. Other materials for producing the above mentioned waveguides and holograms include polymers, quartzes, heavy metal oxides, and liquid crystals. Usually, when a waveguide is produced by using a polymer as a raw material a pattern is formed by means of standard photolithographic techniques. Standard lithographic processes are used to define a pattern in a photoresist layer deposited on a chosen substrate. Then an etchant is applied onto the photoresist layer to etch the defined pattern. The photoresist pattern is then etched away using a solvent. This process however is, time consuming, laborious and costly. For these reasons, the production of a homogeneous large-area waveguides is difficult.
Accordingly, a need exists for a relatively fast, precise and low cost technique for making optical device structures, such as waveguides, and holograms.